package 组队竞赛;

import java.util.Arrays;
import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        int n = in.nextInt();
        long res = 0;
        int[] nums = new int[3 * n];
        for (int i = 0; i < 3 * n; i++) {
            nums[i] = in.nextInt();
        }
        Arrays.sort(nums);
        for (int i = n; i < 3 * n; i += 2) {
            res += nums[i];
        }
        System.out.println(res);
    }
}